Summary of Work: Historically, research on genetic and environmental factors affecting reproduction and subsequent development of the offspring has been centered on the female. After a year-long assessment of the world literature, however, the need for an epidemiologic study of male-mediated reproductive outcomes was clear. Therefore we have obtained data from the European Longitudinal Study of Pregnancy and Childhood being conducted at Bristol, England ("ALSPAC"). In the ALSPAC study, more than 7,000 partners of women who delivered infants in Avon County, England during 1991-2 provided lifetime occupational and toxic exposure histories. The infants and their parents will be followed for seven years. We have coded occupational histories of both mothers and father, using the British Standard Occupational Codes, and categorized the self-reported exposures on the job and in the home. Four studies have been completed this year; one is still in progress. One study reports no association of paternal occupation with fetal growth. A paper using maternal occupational data reports the same result (submitted). The concordance between father's and mother's report of his occupation is being examined in the third study, still in progress. A paper on radiation to the gonads for medical purposes reveals a suggestive but non-significant decrease in fetal growth. Finally, a paper on accuracy of exposure recall in women who miscarry was accepted for publication; women reported more exposures before they miscarried than when asked the same questions after the event occurred.